1. Field of the Invention
The present invention relates to a method of and device for processing an image by the pattern matching process wherein an image matched with a templet image is determined.
2. Related Art Statement
In the field of image processing technology, one of the widely known methods is the so-called pattern matching method in which a predetermined image (commonly referred to as "templet image" and this term will be used throughout the specification and claims) is searched from the image zones to be read and used during the following processing sequence. In this method, a certain zone extracted from the image to be read and a templet image are, respectively, partitioned into plural picture elements from which the differences in density of the corresponding picture elements are found, and the sum of the absolute values of the differences for respective picture elements is used as the means for determining the mismatch degree, the zone giving the minimum sum of differences being defined as the matching zone. However, this known method has a disadvantage in that the accuracy thereof becomes inferior when the illumination condition is fluctuated, which affects the accuracy of the measurement operation directly.
In order to overcome the aforementioned disadvantage caused by the fluctuation of the illumination condition. A method has been proposed wherein the interrelationship between the templet image and the image to be read is found and used as the means for determining the matching degree. However, the practice of this method of prior proposal has another disadvantage in that N.sup.2 time multiplication operations and (N.sup.2 -1) time addition operations are required when the number of picture elements in a certain image zone to be read is N.times.N, and that similar operations must be repeated as the image zone to be read is shifted, leading to the result that enormous calculating operations are needed.